Manufacture of coke



United states Patent 3,058,821 Patented Oct. 16, 1962 Free of Delaware No Drawin Filed Feb. 18, 1960, Ser. No. 9,425 8 Claims. (Q1. 75-42) This invention relates to a novel cokable composition and to a process-for making metallurgical coke out of said composition. This invention further relates to cokes made from said novel cokable compositions and to the use of these cokes for the reduction of suitable oxides in blast furnaces to produce iron, ferromanganese and ferrosilicon.

Conventional metallurgical cokes have been produced almost entirely from selected bituminous coals, at times with additions of anthracite fines, in what are known in the trade as by-product, beehive, Knowles, Broad and Curran ovens. In making such conventional cokes, various coals of low, medium, or high volatile content are blended and ground to provide a more or less uniform or homogeneous mixture, which is then placed in the particular coking apparatus.

The coking operation of the present invention is carried out principally in by-product ovens, although it may be carried out in any of the foregoing ovens. By-product coke is made in batteries of 30 to 75 ovens. Each oven is about 40 ft. long, 10 to 14 ft. high, and 14 to in. wide. The ovens are erected parallel to each other and are heated by combustion of gases in fines placed between each oven. The ovens are charged with from 10 to 20 tons of the coal mixture through top ports, closed tightly and subjected to indirect heat by maintaining flue temperatures between about 1600 and 2700" F. Coking temperatures are controlled by careful regulation of combustion of the gas in the fines which assures even heating and uniform coke quality. The heating cycle may be anywhere from 12 to hours depending upon the flue temperatures, type of coal, and the properties desired in the final coke.

Cokes normally produced in by-product ovens are made by coking a blend of high, medium, and low volatile bituminous coalsthe types, number, and amounts of the domponents being selected according to the ultimate properties desired in the coke. The resulting cokes are usually high in ash content (7.5 to 11%), their porosities are usually over and such cokes have shatter values of 80%+2 in. Their apparent specific gravity is normal- 1y about 0.9. When used in blast furnaces such cokes have considerable reactivity towards CO resulting in relatively high percentages of CO in the off gas. Since the function of these cokes is to reduce iron oxides, the ex.ent of the formation of CO in preference to CO measures the efficiency of these cokes and that of the blast furnace. Furthermore, high percentages of such cokes must be added to the charge to compensate for this type of inefiicient carbon usage. This also has the adverse effect of reducing the throughput or melting rate of the blast furnace.

Therefore, in the past practice of reducing oxides in blast furnaces, it has been conventional to strive for, obtain and use cokes having high porosity, low apparent specific gravity, and high reactivity. Cokes having such qualities were also characterized by having thin cell-wall structure and low bulk density. Cokes having such characteristics were accepted as satisfactory or even sought, in the belief that when employing cokes having these qualities, the most highly desired operating conditions for the blast furnace were obtained.

It is contended that the past strivings and practices of those engaged in blast furnace operation for cokes having such previously described characteristics are or were based on a lack of adequate knowledge of the reduction process which actually takes place in a blast furnace, and that when the principles of operating a blast furnace are based objectively on actual coke performance in a blast furnace, it will be appreciated, and those in the art will be persuaded, that much more suitable blast furnace coke has the following characteristics: high apparent specific gravity, thick cell walls, low reactivity, high bulk density and low porosity. These properties are directly opposite to the coke characteristics previously sought or obtained.

It is maintained that with a coke having such new characteristics, much more of the desired reaction in the blast furnace between the coke and iron oxides occurs, resulting in higher percentages of CO (lower CO) in the off gases than with the cokes 0f the prior art and that because of this the coke of this invention is more fully utilized to reduce oxides to iron, ferromanganese and ferrosilicon.

It is generally accepted that in the coke combustion Zone of a blast furnace, reducing gases such as CO and H are formed, which under conventional furnace conditions, react with oxides of iron to form iron, CO and H 0. The CO and H 0 react with coke in accordance with the Boudouard and Water Gas reactions respectively to form CO and H which again react with iron oxide as previously noted. The reaction kinetics of the water gas reaction are such that under furnace conditions the bulk of the H (hydrogen) escapes with the off gases. The reaction kinetics of the Boudouard reaction are such that under conventional furnace conditions, both the CO and CO formed from the iron oxide reaction, escape in the off gases. It is maintained that the use of cokes of this invention, having these newly described characteristics, shifts the Boudouard reaction so that more CO and less CO is present in the 05 gas.

It is further generally accepted that in a blast furnace, in order to produce ferro alloys such as ferromanganese and ferrosilicon, high hearth temperatures are required for the reduction of oxides of manganese and silicon to permit their alloying with iron. It is maintained that the use of cokes of this invention and having these newly described characteristics results in the advantage of higher combustion temperatures. This in turn raises the hearth temperatures and therefore promotes and enhances this desired reduction of manganese and silicon oxides and production of ferromanganese and ferrosilicon along with the iron.

It is another advantage of the coke having these newly described characteristics that it occupies less space in the blast furnace. There is, therefore, more space available for metallic oxide charge or burden in the furnace.

An additional advantage of the higher temperatures reached in the blast furnace combustion zone when using cokes having these new characteristics is that less coke is needed to reduce a given amount of burden or metallic oxide charge than is required when using cokes not having the same qualities.

Additional advantages derived when using cokes having these newly described characteristics, which are the cokes of the present invention, will be described hereinafter.

It is therefore an object of this invention to produce a coke which will substantially reduce coke consumption and increase melting rates in blast furnace practice, particularly when reducing iron, manganese and silicon oxides.

It is a further object of this invention to produce a metallurgical'coke of higher apparent specific gravity, thicker cell walls, reduced porosity, and increased bulk density, giving rise to improved hot strength and burning properties.

It is a further object of this invention to produce a metallurgical coke having a high degree of intense combustibility (higher combustion temperatures) and of-reduced reactivity towards CO to produce CO.

It is a further object of this invention to provide a method for the reduction of iron oxides in blast furnace practice by using the novel coke herein described.

It is a further object of this invention to provide a novel method for coking whereby a novel cokable composition can be utilized in order to effect marked improvement in the resulting blast furnace coke.

It is another object of this invention to provide a novel method for reducing the amount of limestone needed for the reduction of oxides in blast furnace operation by using the novel coke herein described.

It has been found that cokes having all of the foregoing described characteristics accomplishing all of the foregoing objectives and resulting in the many enumerated advantages can be obtained by coking in a coking oven a thoroughly blended mixture of a conventional high volatile (above 33% by weight, average volatile content) coking coal with a petroleum coke having an average volatile content in the range of from about 9 to about 13% by weight. Such conventional high volatile coking coals or blends employed in this invention, and as defined in the claims, may already contain or have added thereto a minor amount of mid volatile coal. In the practice of this invention, no low volatile coal is added. Not only is this advantageous from an economic point of view, but indeed, any addition of low volatile coal leads to results and coke characteristics departing from the teachings of this invention. In the case where the fluidity of the high volatile coal is extremely high, small percentages of anthracite fines (37%) are or may be added to make up the high volatile coal constituent in order to absorb this extra fluidity. In the case where the high volatile coal lacks sufiicient fluidity for producing metallurgical coke, it is fortified with medium volatile coals to make up the high volatile coal constituent. It is necessary, however, to the obtainment of the cokes of this invention that the petroleum coke in the coking blend first be ground or comminuted to such an extent that substantially all or at least 90% of it passes through a inch screen. It is also necessary that the petroleum coke having these characteristics be used in a percentage of not less than about 5% and not more than about 20% by weight of the total coking mixture. As aforesaid minor percentages of anthracite fines or of mid or medium volatile coals (volatile content between 22 and 33% by weight) may be used in conjunction with or as a part of the high-volatile coal component, of the coking mixture.

For preferred results the high-volatile blend coal component of the coking mixture is also diminished in size to the size normally employed in making cokes with low volatile coals, viz. to Where all' or a high percentage,

such as about of said high volatile coal component passes through a M1 inch screen after grinding.

The coke is discharged from the ovens in a hard solid state and of good size and is adapted to carry a heavy burden which makes it particularly suitable for use in blast furnace operations.

It is to be understood that the present invention in regard to the process for the production of the high grade blast furnace coke may utilize temperatures ranging from about 1600 to about 2700 F. and the coking time may be varied from about 14 to about 72 hours depending upon the production rate desired from the coking ovens which dictates the temperature employed. These factors such as temperature and heating time depend upon the size of the retort and oven used, the quantity of the charge and similar factors which maybe varied as desired.

It is believed that the improved results in blast furnace practice obtained by using the coke of this invention are due to a combination of the physical and chemical properties of this novel coke including high apparent specific gravity, and thick cell walls resulting in high hot strength (hot strength is the compressive strength of the coke when the coke bed is heatedto the temperature of the blast furnace). The thick cell walls of the coke of this invention will not collapse at high blast furnace temperatures, so that a more uniform coke size is provided in the combustion zone resulting in more uniform combustion in the blast furnace thus minimizing temperature fluctuations and resulting in more uniform operations.

The coke of this invention also has a higher combustion temperature than regular blast furnace coke. Because of the higher temperatures obtained, the considerably reduced reactivity, and the increased hot strength, the blast furnace reactions are much more elficient, and

' therefore less coke is used for the reduction of iron oxides when using the coke of this invention than when using cokes of the prior art.

This mixture is then placed in a suitable coking oven such as a byproduct oven which has been described above, and a description of which may also be found in the Coking Section of the Encyclopedia of Chemical Technology, volume 3, the Interscience Encyclopedia, New York, 1949. a

The blend of high volatile coal and petroleum coke is charged to the aforesaid coking apparatus, which is sealed against admission of air as in normal coking practice, and is then subjected to coking temperature until coking action is completed, producing the desired hard, dense, metallurgical coke. The oven temperature depends upon length of coking time, width of oven, ca-' pacity of oven and other factors. For a given rate of oven operation, the oven Wall may have a temperature of about 2100" F. and a heating flue temperature of about 2300 F. However, the effective temperature of coking will vary widely depending upon the desired production rate and is adjusted to a given rate, as in ordinary coking operations, to produce a high grade blast furnace coke high in fixed carbon, low in volatile matter and ash and with a sulfur content adapted to the intended purpose. The resulting coke is a product fundamentally distinct from the petroleum coke and high volatile coal and any other ingredients of the raw material mixture, in that it is higher in fixed carbon, much lower in volatiles and much harder and firmer in structure with an excellent crushing strength or structural stability.

The coke may be discharged from the ovens without difiiculty after the oven vents are opened and is pushed into a quenching car or other receptacles where it is quenched, usually with water, in accordance with ordinary coking pnactice.

The petroleum cokes employed in making the cokes which are 'the subject of this invention result from the thermal cracking and polymerization of heavy petroleum residues such as reduced or top crudes, thermally or catalytically cracked residuums, etc. The coking is normally conducted in a vertical cylindrical drum such as those manufactured by Kellogg, Lummus and Foster Wheeler Companies. The heavy hydrocarbons are admitted into the drum at a temperature between 875 and 950 F. and are permitted to soak and carbonize until the drum is nearly filled with a solid coke. This material is removed from the drum by various decoking methods known to the art. Only petroleum cokes having a volatile matter content averaging from about 9 to about 13% by weight and which are made in such delayed cokers are employed in the present invention.

The volatile matter being discussed here is determined by ASTM method D 271-48 modified for sparking fuels and is exclusive of the moisture and free oil which would be removed by heating to temperatures of 400- 500 F. Volatile matter is determined in a platinum crucible in an electrically heated furnace maintained at temperatures of 1742 F.i36 F. A one gram sample of dry 60 mesh coke is preheated at temperatures below 1742 F. and then kept at a temperature of 1742 F.i36 F. for 6 minutes and the resulting weight-loss is termed volatile matter.

Also, the petroleum coke used in making the blast furnace cokes of the present invention must have a particle size of at least 90% -%s in.

It is known that to produce a satisfactory coke the raw materials employed must possess a certain amount of blocking qualities and a certain amount of fluidity qualities. Without suflicient blocking characteristics, coke produced is small 'and described in the art as fingery and brittle. Physical tests performed on such cokes show them to give low stability, low shatter and high hardness test results. Without suthcient fluidity, coke produced would be described in the art as sandy, pebbly or soft. Neither type would exhibit sufficient size or strength to be a satisfactory blast furnace fuel.

The prior art in making a coke possessing the required size and strength depends or depended upon low volatile coal as a prime ingredient. When this is blended with the proper proportion of contracting high volatile coking coal to control the dangerous pressures associated with the use of low volatile coal, a nicely sized strong coke is produced. However, due to the low volatile coals property of expansion, a very light, thin cell walled coke with high reactivity and porosity is produced.

Without in any way being bound by theoretical explanations it is believed that on heating delayed coker raw petroleum coke having the aforedescribed requisite size and volatile matter characteristics to temperatures between 400 and 500 C., the surface of the petroleum coke particles becomes semi-plastic or active in such a way that the particles are much more easily wetted and absorbed by the fluid components of the high volatile coal. This wetting or absorption does not appear to (in any way) interfere with the intrinsic fluidity of the coals used, such that the coal still forms the typical cell like structure, called coke, in its finished form. In other words, it appears that the distinguishing feature of coke formed by use of petroleum coke having the aforementioned properties is that the petroleum coke particles act as reinforcement of the Walls in the cell structure of the final metallurgical or blast furnace coke, thus contributing to increased cell wall thickness and to the required size, strength, and density of the finished product. This combining of the two materials into a coke may be termed a transformation which results in a solid solution. ln this transformation several well-known processes are probably taking place either singly or in combination, such as agglomeration, agglutination, coking, aromatization, peptizing, partial digestion, intumescense, fusion, and inclusion of filler, etc.

Regardless of which of the foregoing processes predominate and of what the actual phenomena occurring are, it is known that metallurgical cokes having the aforedescribed new and desired characteristics are obtained and that such cokes also possess desired additional characteristics such as are required to satisfactorily pass conventional shatter, stability, and hardness tests. That this is the case is evidenced by the several facts and experimental results which follow.

The thicker cell walls attributed to the novel coke are recognized by the following factors: Weights of the pieces of the novel coke are heavier than the same size pieces of normal coke as determined by apparent specific gravity and bulk density tests. Since there is no corresponding increase in the true specific gravity of the carbon particles as measured by standard methods, then obviously the cell walls of the coke must be thicker to account for the added weight. Coke cell space calculations by ASTM methods as well as actual microphotographs of cell Wdl structure also confirm the presence of thicker cell walls.

Details of the tests used in measuring the properties of the novel coke can be found in the booklet published by the American Society for Testing Materials titled ASTM Standards on Coal and Coke, prepared by Committee D-S and issued September 1957 (pages 103405 and page 113).

In the apparent specific gravity test (ASTM D167-24) a sample of dry coke of standard size and known weight is immersed in water with standard conditions such that all water displaced and absorbed can be weighed. The apparent specific gravity thus equals Weight of dry coke Total wt. (displaced and absorbed) water The test for porosity or cell space uses the results of the two previous tests as follows:

Percent cell space 100 (Apparent specific gravity True specific gravity Cubic foot weights or bulk densities are obtained by directly weighing a standard volume of coke obtained under standard conditions. Total weight of coke is then divided by the standard volume to determine the cubic foot weight of the coke.

The 2 inch shatter is determined by ASTM method D 141-48 and consists of dropping approximately a 50 lb. sample of coke 2 in.) four times upon a heavy steel plate from a height of 6 feet. A screen analysis is made of the broken material and the result obtained is the percent coke retained on the 2 inch screen. This percentage is used as an index of strength.

Table I shows experimental results obtained as regards apparent specific gravity, porosity, bulk density and 2" shatter when making blast furnace cokes out of the compositions of this invention and also contrasts these with results obtained for prior art cokes employing low volatile coal rather than the petroleum coke of this invention. Four diflerent high volatile coal systems are set forth in order to demonstrate the universality and the consistency of the improvements obtained. In other words, cokes made from any given starting high volatile coal is improved by the use of the petroleum coke of this invention in the place of low volatile coal.

In all of the examples of Table I, the petroleum coke was of the proper particle size and volatile matter content.

Table II, following, shows the importance of proper particle size and its effect on coke quality as demonstrated by comparative shatter, stability and hardness test results.

In the tumbler test, ASTM method D-294-50, which provides a relative measure of resistance of the coke to degradation by abrasion and to a certain extent is influenced by the effect of impact, samples of a size range of from 2 to 3 inches are weighed and then tumbled in a drum rotating at about 25 r.p.m. for 1400 revolutions. The coke is then sieved successively on screens of 2, 1.5, 1.06, 0.530, and 0.265 inch openings and each fraction separately weighed. The stability factor is the percent of coke retained on the 1.06 inch sieve and the hardness factor is the percent retained on the 0.265 inch sieve.

and as a result, coke of inferior strength is or would be produced. If its volatile content is above about 13% then the surfaces of the petroleum coke particles at 400 to 500 C. become more active than is desirable in the present invention. As a result the particles are more completely absorbed by the high volatile coal blend and do not contribute sufliciently to the blocking up requirements necessary to produce a coke of adequate size suitable for blast furnace operation. This type of a coke would also be brittle and physical tests would show low stability and low shatter results.

As previously stated the percentage of 913% volatile content petroleum coke employed in the present invention should comprise from about to about 20 percent of the TABLE I Comparison of Novel Coke Wzth Normal C okc Blend composition ASTM test Percent D-167-24 Percent decrease Furnace coke produced from- High vol. Petro- Low vol. D-292-29, D-141-48 increase in cell blend leum coal, pounds 2" in ASG 1 space 2 coal, coke, percent Cell per cu. ft. shatter, percent percent ASG 1 space, eu. it. percent percent Western coals:

Normal blend 90 0.85 56. 7 55. 6 Novel blend 92. 5 7. 5 0. 94 52.9 56. 2 11 7 Colorado coals:

Normal blend. 85 O. 96 50 26. 5 71. 4 Novel blend 88 12 1.06 45 29. 5 72. 2 4 10 11 Illinois coals:

Normal blend 80 0. 80 58 79. 9 Novel blend 80 20 0. 89 53 81. 6 11 9 Utah coals:

Normal blend 90 10 0.75 Novel blend 95 5 0. 82 9 1 Apparent specific gravity.

2 Also referred to as porosity.

3 Also referred to as bulk density.

4 Note the percent increase in pounds per cubic ft. calculates to 11%.

TABLE II E fleet of Pet. Coke Pzllverization on Coke Quality As previously stated, the petroleum coke employed in the present invention should have a volatile content from about 9 to about 13% and should also be that type of petroleum coke as is obtained from a delayed coker. Relative to this, no special processing is required in order to obtain the petroleum coke from the delayed coker refinery operation. This is contrary to prior art methods of making coke, which utilize petroleum coke as an ingredient in their coka ble composition, which employ higher volatile content delayed coker petroleum coke, making it necessary to change the normal process variables at the refinery.

The use of petroleum coke having the foregoing volatile content of 9 to 13% is important not only because of the foregoing advantage but also because of the fact that if its volatile content is below about 9%, the surfaces of the petroleum coke particles donot become sufficiently semi-plastic" or active when the particles are heated to temperatures between 400 and 500 C. The particles therefore are less easily wetted and absorbed by the fluid components of the high volatile coal coking blend. The percentage of petroleum coke used within this range is dictated by the characteristics of the normal high volatile blending coal used, the principal of which are its fluidity and blocking up characteristics. These characteristics vary but are inherent in each particular coal depending onthe conditions and extent of coalification of the vegetable matter from which the coal was formed. In such coking coals and increase in fluidity results in small coke, while a reduction in fluidity results in large, poor strength coke, Which easily breaks up. In the proper range of fluidity with proper amount of petroleum coke, a coke of satisfactory size and strength is produced. The amount of petroleum coke added to high volatile blend coals is therefore dependent on the amount that can be absorbed in the cell Walls formed on coking high volatile blend coal and still result in coke of satisfactory size and strength. A high volatile blend coal with low fluidity cannot absorb much petroleum coke. 'If less than 5 percent are absorbed then the coke produced will be unsatfisctory in that it will have low strength characteristics and therefore break up into pieces too small for satisfactory blast furnace operation.

If more than 20 percentpetroleum coke are absorbed then the coke produced will be unsatisfactory in that it will be too large and soft for satisfactory blast furnace operation. Cell wall reinforcement also would not be evident since the ability of the high volatile coal to form true coke cells would be impaired by the excess petroleum coke.

Also, as previously stated, it is important that the petroleum coke of this invention be the sole or substantially the sole low volatile ingredient employed with the high volatile blend coal of the cokable mixture. .This is evident from the data shown in the following table.

stating that indirect reduction is Effect of Low Volatile Coal n Novel Coke Characteristics Blend ASTM test (D-167-24) Increase Decrease Furnace coke produced from in in ce Eastern coals High vol. Petro- Low vol. ASG, space,

blend leurn coal, Cell percent percent coal, coke, percent ASG 1 space 2 percent percent With low volatile coal 81.1 12. 9 6.0 1.17 39. \Vithout low volatile coal 86. 7 13. 3 1. 25 34. 5 6 13 1 Apparent specific gravity. 2 Also referred to as porosity.

From the above table it is evident that low volatile coals have a substantial deleterious effect on coke density and porosity. That this is so can also be demonstrated with microphotographs. These results are due to the fact that low volatile coals, when used as blocking agents, open up the cell structure of the resulting coke, and further to the fact that petroleum coke particles on becoming active at 400500 C., are not as readily absorbed in the high volatile coal cell walls in the presence of low volatile coals as they are otherwise.

Several advantages are obtained when following the teachings of this invention, some of which have already been alluded to. These are:

(1) More hard to reduce ores may comprise part of the burden, because of the higher hearth temperatures obtained.

(2) There is a decrease in the amount of limestone required in the ore reduction process. Approximately percent less limestone is required for each ton metal produced than is required with prior art cokes. It was found that even with either lowered alkalinity of the slag or lowered slag volume, when using the novel cokes of this invention, normal sulfur and silicon contents in the metals produced are obtained. This again demonstrates that higher temperatures are obtained in the combustion zone of the blast furnace.

(3) Because the novel cokes are about 10% heavier than normal cokes and as a result occupy about 10% less volume in the furnace, there is a considerable increase in iron oxides (approximately -25% in the furnace. This iron oxide packing promotes more efficient heat transfer and longer contact time with available reducing gases.

(4) The carbon dioxide in the off gas from the blast furnace is increased about 8 percent indicating more efiicient carbon use compared to former cokes, which give less carbon dioxide and a higher percentage of carbon monoxide in the off gas. This is another way of favored with the novel coke. To the extent that a higher proportion of oxygen from the ore combines with carbon from the coke, the more efiiciently the novel coke is utilized. This phenomenon also contributes to less coke usage.

(5) Approximately 100 to 200 pounds less coke is required to produce a ton of iron than is required when using corresponding prior art cokes.

(6) Because of the higher hearth temperatures experienced the reduction of oxides of manganese and silicon is promoted resulting in reduction of coke usage in the production of ferromanganese and ferrosilicon in a blast furnace.

Having thus described and exemplified my invention but intending to be limited only by the scope of the appended claims, I claim:

1. A composition for the production of metallurgical coke consisting essentially of from about ninety-five to about eighty percent of a high-volatile coking coal and from about five to about twenty percent of raw petroleum coke from a delayed coker, said petroleum coke having an average volatile matter content of from about 9 to about 13% by weight and a particle size such that at least about of said coke passes a /8 inch screen.

2. A composition according to claim 1 wherein the particle size of the high-volatile coking coal is such that at least about 90% of its passes a inch screen.

3. A process for manufacturing metallurgical coke which comprises: forming an intimate mixture consisting essentially of from about ninety-five to about eighty percent of a high-volatile coking coal and from about five to about twenty percent of raw petroleum coke having a volatile matter content of from about 9 to about 13% by weight and an average particle size such that at least about 90% of said coke passes a /s inch screen, and subjecting the mixture to coking temperatures in a coking zone until coking action is completed.

4. The process of claim 3 further characterized in that at least about 90% of the particles of the coking coal pass a inch screen.

5. The blast furnace coke formed by the process of claim 3.

6. The blast furnace coke formed by the process of claim 3 and being further characterized by having apparent specific gravity and bulk density values approximately 10% higher, cell walls thicker, and a porosity about 9% lower than obtained when employing low volatile coal instead of the petroleum coke.

7. In a process for producing a material selected from the group consisting of iron, ferromanganese, ferrosilicon and mixtures thereof in a blast furnace wherein a charge comprising coke and the suitable oxides are heated to reduce said oxides to metallics by oxidation of said coke, the method which comprises reducing said suitable oxides with a metallurgical coke made from the cokeable composition of claim 1.

8. In a process for producing a material selected from the group consisting of iron, ferromanganese, ferrosilicon and mixtures thereof in a blast furnace wherein a charge comprising coke and the suitable oxides are heated to reduoe said oxides to metallics by oxidation of said coke, the method of increasing combustion temperatures and increasing the volume of suitable oxides in the working volume of said blast furnace which comprises reducing said suitable oxides with a metallurgical coke made from the cokeable composition of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 614,852 Etter Nov. 29, 1898 1,815,918 Knowles July 28, 1931 2,640,016 Martin May 26, 1953 2,787,585 Lohrey Apr. 2, 1957 2,808,370 Bowers Oct. 1, 1957 FOREIGN PATENTS 737,063 Great Britain Sept. 21, 1955 

1. A COMPOSITION FOR THE PRODUCTION OF METALLURGICAL COKE CONSISTING ESSENTIALLY OF FROM ABOUT NINETY-FIVE TO ABOUT EIGHTY PERCENT OF A HIGH-VOLATILE COKING COAL AND FROM ABOUT FIVE TO ABOUT TWENTY PERCENT OF RAW PETROLEUM COKE FROM A DELAYED COKER, SAID PETROLEUM COKE HAVING AN AVERAGE VOLATILE MATTER CONTENT OF FROM ABOUT 9 TO ABOUT 13% BY WEIGHT AND A PARTICLE SIZE SUCH THAT AT LEAST ABOUT 90% OF SAID COKE PASSES A 1/8 INCH SCREEN. 